Text integrity & AI-use detection you can actually interpret.
CopyCat is a local, on-device self-audit tool. It analyzes writing from multiple angles and returns a likelihood estimate with a short explanation you can act on.
Important: CopyCat provides a likelihood estimate, not proof. Use it to revise and reduce risk, not to “win” against any detector.
Download CopyCat
These are native desktop builds for macOS and Windows. No terminal setup required. CopyCat runs entirely on-device and is intended for individual evaluation, research, and demonstration purposes.
*By downloading, you agree we may log your email, IP, and user-agent for abuse prevention and usage metrics.
- Apple Silicon: macOS 13+ (M1/M2/M3)
- Windows (x64): Windows 10 / 11
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shasum -a 256 <file>
(On Windows PowerShell: Get-FileHash -Algorithm SHA256 .\CopyCat-Windows-x64.zip)
- Open CopyCat-mac.dmg (Apple Silicon) or CopyCat-latest-x86_64.dmg (Intel)
- Drag CopyCat.app into Applications
- Open Applications → CopyCat
- Download CopyCatSetup-windows-v0.4.0.exe
- Double click to start CopyCat Installer
127.0.0.1 (random port) and opens the UI in an app window.
Getting started
CopyCat is designed for simple self-audits. Paste a few paragraphs, run the analysis, then read the verdict and the explanation bullets to understand what drove the score.
- Launch CopyCat
- Paste at least 2–4 paragraphs when possible (short samples are harder to judge)
- Click Run analysis
- Use the bullets to revise (vary sentence length, reduce template phrasing, add more original detail)
- Likely human-written: more human-like variation in structure and phrasing
- AI-assisted: mixed signals (common in edited drafts or highly templated writing)
- AI-generated: stronger match to machine-like patterns
Reminder: This is a likelihood estimate, not certainty. Technical writing can score higher because it’s more standardized by nature.
FAQ & troubleshooting
Common questions from students and first-time users.
Why did my writing read as “AI-likely”?
Often it’s because the passage is short, highly standardized (technical / formal), or uses repeated “template” transitions. Try adding more original detail, varying sentence length, and submitting a longer sample.
Does CopyCat prove something is AI-generated?
No. CopyCat provides a likelihood estimate to help you self-audit and revise. It does not produce “proof” and should not be used to accuse others.
What text length works best?
Longer is better. A few paragraphs (200–800+ words) typically gives more stable results than a single short paragraph.
My paper is indented (not double-spaced blank lines). Is that ok?
Yes. Indented paragraphs are still paragraphs. If you paste text and it loses formatting, you can add blank lines between paragraphs for clarity.
Windows says the file is blocked or warns me (SmartScreen).
If SmartScreen appears, click “More info” → “Run anyway.” If you extracted the ZIP, make sure you run CopyCat.exe from the extracted folder.
macOS says the app can’t be opened.
If you see a security prompt, open System Settings → Privacy & Security and allow CopyCat, then try again.
What does “burstiness” mean?
It’s a simple idea: human writing often varies sentence length and rhythm more than templated text. CopyCat uses multiple signals like this to form a likelihood estimate.
Send feedback
If you’re willing, tell me what OS you’re on and what felt confusing. Intel Mac feedback is especially helpful right now.
Email: info@calypso-labs.com
Include: OS + build (Apple Silicon / Intel / Windows) + what you tested + what surprised you.
Try the CopyCat demo
This is a simple front-end demo. Scores here are simulated to illustrate the interface, not represent the full engine.
Demo notice: This section runs entirely in your browser and does not reflect the desktop app’s actual model behavior.